Atomistic Molecular Dynamics Simulations of Cyclic Bottlebrush Polymers

Bottlebrush polymers (BBPs) with cyclic backbones have attracted significant attention due to their unique topological features. Experiments have shown that cyclic BBPs are more compact than their linear counterparts and suppress interpolymer associations. However, they have remained rather unexplored computationally compared to their linear analogs which would otherwise provide molecular details on the morphologies of cyclic BBPs. Using atomistic molecular dynamics simulations we investigate cyclic poly(vinyl alcohol)-graft-poly(ethylene oxide) BBPs (c-PVA-g-PEO) and focus on the side chain length effect. The dependence of the structural properties, shape change, and hydration properties on side chain length are studied. Our results provide scaling laws that describe the dependence of the size of BBPs on graft length in the limit of long and short grafts. We also demonstrate different regimes that determine the stretching of the backbone and the side chains. Moreover, we evaluate the local crowdedness of cyclic BBPs induced by the grafted chains, which affect the loading capacity for cyclic BBPs when used as a carrier.